MUSCLE. 133 



resemble one another in general character j some are more 

 irregular, more granulous, whilst others are relatively smooth. 

 The smoother ones represent cylinders, which are generally 

 more or less flattened (sec pi. IV, fig. 3), in which they are 

 delineated from the brachial muscles of a foetal pig seven inches 

 in length, a representing the flat surface, b the marginal. The 

 cylinder a presents a dark margin, and an internal clear por- 

 tion, a distinction which is yet more manifest in c } where the 

 dark margin is broader and sharply defined on its inner edge, 

 so that it has quite the appearance of a hollow cylinder. 

 I must, however, remark, that but very few fibres present this 

 appearance sufficiently distinct to satisfy the mind of the ob- 

 server. But in many instances it was so manifest, that no 

 other explanation seemed left than to suppose the fibre a hollow 

 tube. In the clear portion of the cylinder, which corresponds 

 to the cavity, (in addition to some small granules,) larger oval 

 corpuscles are seen, which are often very much extended in 

 the longitudinal direction. Their form at once shows them 

 to be nuclei, and they frequently contain one or two nucleoli. 

 The distance at which they lie from one another is more or 

 less regular in different instances. They do not lie in the 

 axis of the fibre, but eccentrically, upon and within the thick- 

 ness of the wall, as is seen when the fibre rests upon its 

 margin. (See the fibre b.) That delineation exhibits a regu- 

 larity in their position, since a nucleus lies upon the one side 

 of the wall, the second on the opposite, and the third again 

 upon the first side, and so on ; such, however, does not appear 

 to be the case in every instance. The nuclei are flat, for 

 when viewed edgeways they have the appearance of mere 

 stripes. The thickness of the wall of the cylinder seems 

 to vary, as is shown by a comparison of a with c. The 

 latter, c, the wall of which is the thicker, already presents an 

 appearance of transverse striae. The nuclei, however, arc also 

 still visible in it, as well as small isolated globules which are 

 contained in its cavity. Muscular fibre docs not present any 

 appearance of a cavity after the period of development before 

 mentioned has passed, but the nuclei remain visible for a long 

 time, lying in the thickness of the fibre, and often project 

 upon the outside in the form of small prominences. 



The other form of muscular fibre is delineated in pi. IV, 



